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91.
Toma L Lescouëzec R Vaissermann J Delgado FS Ruiz-Pérez C Carrasco R Cano J Lloret F Julve M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(23):6130-6145
The preparation, X-ray crystallography and magnetic investigation of the compounds PPh4[Cr(bipy)(CN)4].2 CH3CN.H2O (1) (mononuclear), [[Cr(bipy)(CN)4]2Mn-(H2O)4].4H2O (2) (trinuclear), [[Cr(bipy)(CN)4]2Mn(H2O)2] (3) (chain) and [[Cr(bipy)(CN)4]2Mn(H2O)].H2O.CH3CN (4) (double chain) [bipy=2,2'-bipyridine; PPh4 (+)=tetraphenylphosphonium] are described herein. The [Cr(bipy)(CN)4]- unit act either as a monodentate (2) or bis-monodentate (3) ligand toward the manganese atom through one (2) or two (3) of its four cyanide groups. The manganese atom is six-coordinate with two (2) or four (3) cyanide nitrogens and four (2) or two (3) water molecules building a distorted octahedral environment. In 4, two chains of 3 are pillared through interchain Mn-N-C-Cr links which replace one of the two trans-coordinated water molecules at the manganese atom to afford a double chain structure where bis- and tris-monodenate coordination modes of [Cr(bipy)(CN)4]- coexist. The magnetic properties of 1-4 were investigated in the temperature range 1.9-300 K. A Curie law behaviour for a magnetically isolated spin quartet is observed for 1. A significant antiferromagnetic interaction between CrIII and MnII through the single cyanide bridge [J=-6.2 cm(-1), the Hamiltonian being defined as H=-J(SCr1.SMn+SCr2.SMn] occurs in 2 leading to a low-lying spin doublet which is fully populated at T <5 K. A metamagnetic behaviour is observed for 3 and 4 [the values of the critical field Hc being ca. 3000 (3) and 1500 Oe (4)] which is associated to the occurrence of weak interchain antiferromagnetic interactions between ferrimagnetic Cr2III MnII chains. The analysis of the exchange pathways in 2-4 through DFT type calculations together with the magnetic bevaviour simulation using the quantum Monte Carlo methodology provided a good understanding of their magnetic properties. 相似文献
92.
Diego Colombo Fiamma Ronchetti Antonio Scala Lucio Toma 《Journal of carbohydrate chemistry》2013,32(1):89-94
Abstract Methyl 6-O-butyryl-α-D- and L-glucopyranosides and methyl 6-deoxy-α-D- and L-glucopyranosides have been submitted to lipase catalyzed butyrylation, using porcine pancreatic, Candida cylindracea, and Pseudomonas cepacia lipases in organic solvents. The influence of the orientation of the secondary hydroxyl groups on the regioselectivity of the butyrylation is discussed. 相似文献
93.
The use of a newly synthesized fluorescent probe, ABM (conditional name), to determine changes of membrane composition (fluidity), biomass yield, ethanol productivity, and yield of Zymomonas mobilis under anaerobic conditions was investigated. A strong correlation between ABM spectral characteristics in cell suspension and all obtained parameters was observed. It was concluded that application of ABM is a useful tool to detect temperature-induced changes in the membrane composition of Zymomonas mobilis. 相似文献
94.
95.
96.
Toma Albu 《Journal of Pure and Applied Algebra》2007,208(1):101-106
Abstract Cogalois Theory for arbitrary profinite groups was initiated by T. Albu and ?.A. Basarab [An Abstract Cogalois Theory for profinite groups, J. Pure. Appl. Algebra 200 (2005) 227-250]. The aim of this paper is twofold: firstly, to present the abstract group theoretic versions of various types of Kummer field extensions, and secondly, to show how some basic results of the (Field Theoretic) Cogalois Theory can be very easily deduced from their abstract versions. 相似文献
97.
Perić Mato Nižetić Sandro Garašić Ivica Gubeljak Nenad Vuherer Tomaž Tonković Zdenko 《Journal of Thermal Analysis and Calorimetry》2020,141(1):313-322
Journal of Thermal Analysis and Calorimetry - In this investigation, a T-joint numerical welding simulation of thick steel plates is performed to estimate transient temperature distributions,... 相似文献
98.
A quick method for determination of equilibrium temperature of high temperature reactions, which is inexpensive and suitable for small industrial laboratories, is reported. Reaction of high temperature dissociation of calcium carbonate is used as example for quick method application. The method is based on calorimetric measurement, Hess Law, and thermodynamic calculations. The calibrated calorimeter is used to determine enthalpy change for reactions CaCO3(s)?+?HCl(l), Ca(s)?+?2HCl(l), and CaO(s)?+?2HCl(l). By application of Hess??s energy cycle, enthalpies of formation of calcium carbonate and calcium oxide were determined. Acquired results were used to calculate enthalpy change for carbonate dissociation reaction. Calculated enthalpy change value was used for free energy change in dependence of temperature and also for equilibrium constant in dependence of temperature calculation using equations derived from basic thermodynamic equations. Using this method, equilibrium temperature for calcium carbonate dissociation reaction is found to be equal to 1154.14?K, which confirms accuracy of the method. 相似文献
99.
Proline-derived N-sulfonylcarboxamides efficiently catalyze the asymmetric Mannich reaction of cyclic ketones with N-(p-methoxyphenyl)-protected iminoglyoxylate. Both classical organic solvents and ionic liquids were used as the reaction media. With cyclohexanone, the reaction proceeded with high enantioselectivity (99% ee). Enamine intermediates were investigated by DFT calculations. 相似文献
100.
Liquid explosives pose a threat to security on airplanes and other public places, since they can easily be concealed as benign
liquids. A detector, able to quickly identify liquids, would increase the possibility to detect such threats and speed up
security checks. As a step towards a long-term goal to develop a liquid explosive detector, we have constructed an experimental
setup based on a low-cost 1.1 T permanent magnet with huge static magnetic field gradient of 4.8 T/m, which allows us to measure
proton relaxation times T
1 and T
2 and the self-diffusion coefficient D in liquid samples in a thin slice excited by radio-frequency pulses. We have developed a simple model in order to explain
diffusion-enhanced non-exponential magnetization recovery in inversion recovery T
1 experiment in this setup. Measuring a wide variety of liquid samples, we have demonstrated that it is possible to discriminate
between the liquids based solely on these parameters. We discuss further improvements to the detection method, among those
the choice of magnetic field, based on the fast field-cycling measurements. 相似文献